This invention is directed to laminate panels which include a polyimide-based aerogel layer, at least one facesheet layer, and a reflective protection layer on the facesheet. The aerogel layer functions both to insulate and structurally support the panel.
Aerospace panels are difficult to design and produce. The nature of aerospace travel presents environmental stress on panel materials which are far beyond the stress faced in typical applications of those materials. Materials used in the design of aerospace paneling must therefore be durable enough to withstand the extreme conditions in those stressful environments. The nature of aerospace travel also requires that paneling materials be as light as possible. Small differences in the density and weight of these materials can have significant effects on the functionality of the panel, as well as the functionality and energy efficiency of the aerospace device as a whole. Thus, structural and insulating materials in aerospace panels must be selected and optimized for the specific challenges found in aerospace travel.
Aerogel composites have physical and chemical properties which can potentially be optimized to withstand the demands of aerospace panel design. Aerogels describe a class of materials based upon their structure; namely low density, open cell structures with large surface areas (often 900 m2/g or higher) and sub-nanometer scale pore sizes. Aerogels can be prepared by replacing the liquid solvent in a wet gel with air, without substantially altering or collapsing the network structure (e.g., pore characteristics) or the volume of the gel body. Supercritical and subcritical fluid extraction technologies are used to extract the fluid from the gel without causing the collapse of the pores. A variety of different inorganic and organic aerogel compositions are known. Inorganic aerogels are generally based upon metal alkoxides and include materials such as silica, carbides, and alumina. Organic aerogels include carbon aerogels and polymeric aerogels such as polyimides.
Aerogels function as thermal insulators primarily by minimizing conduction (low density, tortuous path for heat transfer through the nanostructures), convection (very small pore sizes minimize convection), and radiation (IR suppressing dopants may easily be dispersed throughout the aerogel matrix). Depending on the formulation, aerogels can function at temperatures of 550° C. and above. Low to moderate density aerogel materials (typically in the range of about 0.01 g/cm to about 0.3 g/cm) are widely considered to be the best solid thermal insulators, and have thermal conductivities of about 12 mW/m-K and below at 37.8° C. and atmospheric pressure.
Aerogels can also be fiber reinforced during production to provide significant structural stability and resilience, particularly in high flexural strain applications. The flexibility of thin aerogel sheets (typically between about 0.1 mm and about 25 mm) allows for the manufacture of large sections of aerogel composites which retain most of the useful qualities of aerogels, such as low density and low thermal conductivity.
A need thus exists for structural and insulating materials which have the strength, thermal conductivity, and density properties to allow for optimized design and manufacturing of aerospace panels. Specifically, a need exists for optimized aerogel materials which have strength, thermal conductivity, and density properties that allow for effective design and manufacturing of aerospace panels. A need also exists for laminate aerospace panels which effectively incorporate the optimized aerogel materials.